The Science of Discworld Revised Edition

Archchancellor. ‘Gods have turned up while our back was turned. There can be no other explanation.’
    ‘Then they seem rather unambitious,’ sniffed the Senior Wrangler. ‘I mean, you’d expect humans, wouldn’t you? Not … blobs you can’t see. They’re not going to bow down and worship anyone, are they?’
    ‘Not where they are,’ said Ridcully. ‘The planet’s full of cracks! You shouldn’t get fire
under
water. That’s against nature!’
    ‘Everywhere you look, little blobs,’ said the Senior Wrangler. ‘Everywhere.’
    ‘Blobs,’ said the Lecturer in Recent Runes. ‘Can they pray? Can they build temples? Can they wage holy war on less enlightened blobs?’
    Ponder shook his head sadly. H EX ’s results were quite clear. Nothing solid could cross the barrier into Roundworld. It was possible, with enough thaumic effort, to exert tiny pressures, but that was all. Of course, you could speculate that thought might get in there, but if that was the case the wizards were thinking some very dull thoughts indeed. ‘Blobs’ wasn’t really a good word for what were currently floating in the warm seas and dribbling over the rocks. It had far too many overtones of feverish gaiety and excitement.
    ‘They’re not even moving,’ said Ridcully. ‘Just bobbing about.’
    ‘Blobbing about, haha,’ said the Senior Wrangler.
    ‘Could we … help them in some way?’ said the Lecturer in Recent Runes. ‘You know … to become better blobs? I fear we have some responsibility.’
    ‘They may be as good as blobs get,’ said Ridcully. ‘What’s up with that Rincewind fellow?’
    They turned. In its circle of smoke, the suited figure was making frantic running motions.
    ‘Do you think, on reflection, that it might not have good idea to miniaturize his image in Roundworld?’ said Ridcully.
    ‘It was the only way we could get him into that little rock pool H EX wanted us to look at, sir,’ said Ponder. ‘He doesn’t
have
to be any particular size. Size is relative.’
    ‘Is that why he keeps calling out for his mother?’
    Ponder went over to the circle and rubbed out a few important runes. Rincewind collapsed on the floor.
    ‘What idiot put me in
there
?’ he said. ‘Ye gods, it’s awful! The size of some of those things!’
    ‘They’re actually tiny,’ said Ponder, helping him up.
    ‘Not when you are smaller than them!’
    ‘My dear chap, they can’t possibly
hurt
you. You have nothing to fear but fear itself.’
    ‘Oh, is that so? What help is that? You think that makes it better? Well, let me tell you, some of that fear can be pretty big and nasty –’
    ‘Calm down, calm
down
.’
    ‘Next time I want to be big, understand?’
    ‘Did they try to communicate with you in any way?’
    ‘They just flailed away with great big whiskers! It was worse than watching wizards arguing!’
    ‘Yes, I doubt if they are very intelligent.’
    ‘Well, nor are the rock pool creatures.’
    ‘I’m just wondering,’ said Ponder, wishing he had a beard to stroke thoughtfully, ‘if perhaps they might … improve with keeping …’

TWENTY-FOUR
DESPITE WHICH …

    THAT BLUE IN the Roundworld sea isn’t a chemical – well, not in the usual ‘
simple
chemical’ sense of the word. It’s a mass of bacteria, called cyanobacteria. Another name for them is ‘blue-green algae’, which is wonderfully confusing.
Modern
so-called blue-green algae are usually red or brown, but the ancient ones probably
were
blue-green. And blue-green algae are really bacteria, whereas most other algae have cells with a nucleus and so are not bacteria. The blue-green colour comes from chlorophyll, but of a different kind from that in plants, together with yellow-orange chemicals called carotenoids.
    Bacteria appeared on Earth at least 3.5 billion years ago, only a few hundred million years after the Earth cooled to the point at which living creatures could survive on it. We know this because of strange layered structures found in sedimentary rocks. The layers can be flat and bumpy, they can form huge branched pillars, or they can be highly convoluted like the leaves in a cabbage. Some deposits are half a mile thick and spread for hundreds of miles. Most date from 2 billion years ago, but those from Warrawoona in Australia are 3.5 billion years old.
    To begin with, nobody knew what these deposits were. In the 1950s and 1960s they were revealed as traces of communities of bacteria, especially